a) Leaving group near the ring

The ring expels the leaving groups that are in a neighboring position, this position being attacked by the nucleophiles in the middle.
derivatives pyrrole thiophene furan 01
The reaction takes place whether the chain is in position 2 or position 3.
derivatives pyrrole thiophene furan 02
b) Carboxylic acids
Carboxylic groups in position 2 or 3 of the ring decarboxylate on heating
pyrrole thiophene furan derivatives 03
c) Hydroxy derivatives
The keto form is more stable than the enol form in both positions 2 and 3.
pyrrole thiophene furan derivatives 04
d) Carbonyls
The carbonyl group attached to the pyrrole ring is not very reactive towards nucleophiles due to the transfer of charge by the ring.
pyrrole thiophene furan derivatives 05